(1) Field of the Invention
The present invention relates to a technology for building a good-quality communication route when performing wireless communications.
(2) Description of the Related Art
Among network technologies is an ad hoc network technology for dynamically building a wireless multi-hop network among nodes. In an ad hoc network, each node has a packet relay function and sends or forwards packets according to its routing table so as to perform multi-hop communications. Wireless multi-hop networks, in which a wireless link between adjacent nodes is detected by exchanging routing packets, have had a problem that a link of no good quality can be used when exchanging routing packets, due to variations in the state of wireless communications over a link caused by the surrounding circumstances and movement of each node. To counter this problem, there has been provided a technology that determines the quality of a link between adjacent nodes depending on the bit error rate to detect a link between adjacent nodes (see Japanese Patent Laid-Open No. 2005-523619).
Also, among link stability determining methods disclosed in a technical document RFC 3626 (T. Clausen, P. Jacquet, “Optimized Link State Routing Protocol (OLSR)” 2003/10) published by the Internet Engineering Task Force (IETF) is link hysteresis. This is a method for determining the stability of a link from routing packets that are intermittently arriving, when the state of wireless communications of the link cannot be obtained.
Wireless local area networks (LAN) allow the threshold of the reception radio wave intensity to be set up, thus creating a mechanism in which a packet whose radio wave intensity is lower than the threshold will be discarded.